Commercial aircraft typically utilize a gas turbofan engine mounted under wing or in a tail structure. The gas turbine engine typically includes a fan section, and a core section including a compressor section, a combustor section and a turbine section all rotating about a common axis. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section.
The fan section drives air through a bypass passage to develop a majority of thrust produced by the engine. Larger fan diameters increase engine efficiencies. Increased diameters require correspondingly large cases and nacelle structures that are currently mounted under an aircraft wing. Accommodations such as longer landing gear, cantilevered engine mounting structures and/or complex wing structures required due to the larger fan sections increase weight and counteract the engine efficiency gains.
Accordingly, engine and aircraft manufactures continue to seek further improvements to aircraft design to take advantage of advances in engine performance including improvements to thermal, transfer and propulsive efficiencies.